An increasing problem with communication links has arisen for digital communications on wafers, between wafers, on printed circuit boards and in cabinets with the growing demands on speed and powerfulness for the kind of electronic applications using the mentioned kind of techniques. A particular application is in digital electronic equipment, such as digital computers. The communication link according to the invention has been developped for transmission across distances of the order of a few mm in a chip.
Most improvements have been in the hardware. The introduction of VLSI and the enhancement in lithography has made it possible to build computers on only a chip that five years ago were super computers. The dimensions have shrunk exponentially and is now less than 1 micrometer. The clock rate as well as the number of active transistors have increased many orders of magnitude. When the packing density has been very tight and the operation speed has become extremely high, then wires of a few mm in such a chip have been very sensitive to disturbances both from external noise sources and from the internal circuits.